WO2008012225A1 - Binary fluorescent pigment composition and its use for forgery and counterfeit prevention - Google Patents

Binary fluorescent pigment composition and its use for forgery and counterfeit prevention Download PDF

Info

Publication number
WO2008012225A1
WO2008012225A1 PCT/EP2007/057305 EP2007057305W WO2008012225A1 WO 2008012225 A1 WO2008012225 A1 WO 2008012225A1 EP 2007057305 W EP2007057305 W EP 2007057305W WO 2008012225 A1 WO2008012225 A1 WO 2008012225A1
Authority
WO
WIPO (PCT)
Prior art keywords
fluorescent
light
wavelength
visible light
irradiation
Prior art date
Application number
PCT/EP2007/057305
Other languages
French (fr)
Inventor
Thomas Bolle
Christian Fabian
Hans Reichert
Bernhard Seider
Original Assignee
Ciba Holding Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ciba Holding Inc. filed Critical Ciba Holding Inc.
Publication of WO2008012225A1 publication Critical patent/WO2008012225A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M3/00—Printing processes to produce particular kinds of printed work, e.g. patterns
    • B41M3/14—Security printing
    • B41M3/144—Security printing using fluorescent, luminescent or iridescent effects
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7728—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing europium
    • C09K11/7734—Aluminates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/02—Compounds of alkaline earth metals or magnesium
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/50—Sympathetic, colour changing or similar inks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7783—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals one of which being europium
    • C09K11/7784—Chalcogenides
    • C09K11/7787—Oxides
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7783—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals one of which being europium
    • C09K11/7794—Vanadates; Chromates; Molybdates; Tungstates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7783—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals one of which being europium
    • C09K11/7795—Phosphates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values

Definitions

  • the present invention relates to binary fluorescent pigment compositions, products containing them and their use for forgery and counterfeit prevention.
  • the invention relates to a luminous ink comprising two fluorescent pigments that emit light upon irradiation by ultraviolet light and an ink vehicle, wherein the first fluorescent pigment emits light of a first wavelength in a visible light range upon irradiation by an ultraviolet light of a first wavelength and is substantially transparent to visible light, and the second fluorescent substance that emits light of a second wavelength in a visible light range being different from the first wavelength in a visible light range upon irradiation by an ultraviolet light of a second wavelength and is substantially transparent to visible light.
  • the fluorescent luminous ink is difficult to identify by sight in the presence of visible light and becomes identifiable by sight by emitting light in a visible light range upon irradiation by ultraviolet light.
  • US5005873 relates to an article comprising a substrate having markings which are provided by at least two fluorescent materials which have different excitation spectra in the ultraviolet region of the spectrum and different emission spectra in the visible region of the spectrum. US5005873 also provides a method of marking an article for identification. While inorganic phosphors are mentioned as examples of fluorescent materials, US5005873 fails to disclose their particle sizes.
  • US2004251833 relates to a plasma display apparatus, and more particularly to fluorescent material coated onto a fluorescent layer which is a part of the plasma display apparatus.
  • the fluorescent material is coated on sidewalls of the partition walls and an exposed surface of an dielectric layer.
  • the fluorescent material converts ultra-violet rays generated by discharges, into visible lights. For instance, red, green and blue (RGB) fluorescent materials are coated every three cells, ensuring displaying color images.
  • RGB red, green and blue
  • US2002063301 discloses a semiconductor light-emitting device constituted by mounting a semiconductor light-emitting element on a base substance, wherein the semiconductor light- emitting element has outgoing light having an emission wavelength of 390 to 420 nm; and there is included a fluorescent substance that is excited by outgoing light from the semiconductor light-emitting element and emits red light having an emission wavelength with its main emission peak in a wavelength range of 600 to 670 nm.
  • fluorescent substances are M 2 O 2 S: Eu (M is any one or more elements selected from La, Gd and Y); 0.5MgF 2 3.5MgO GeO2: Mn; Y 2 O 3 : Eu, Y(P, V)O 4 : Eu; etc.
  • WO2006072919 discloses an illumination system comprising a radiation source and luminescent material comprising a phosphor of general formula (Bai. ⁇ Sr x ) 1-a Mg 3- b AI 14 O 25 :EU a Mn b! wherein 0 ⁇ x ⁇ 1 , 0 ⁇ a ⁇ 0.2, 0 ⁇ b ⁇ 0.2, a + b > 0.
  • fluorescent luminous ink is ink that is hardly identifiable by the naked eye in the presence of ordinary visible light but becomes visible to the naked eye upon irradiation by ultraviolet light or infrared light, making it possible to detect the image by sight.
  • the technology has been well known in the art.
  • a first aspect of the present invention relates to a pigment composition
  • a pigment composition comprising a first and a second inorganic fluorescent pigment that emit light upon irradiation by ultraviolet light, wherein the first fluorescent pigment emits light of a first wavelength in a visible light range upon irradiation by an ultraviolet light of a first wavelength and is substantially transparent to visible light, and the second fluorescent pigment that emits light of a second wavelength in a visible light range that is different from the first wavelength in a visible light range upon irradiation by an ultraviolet light of a second wavelength and is substantially transparent to visible light and wherein the first and the second inorganic fluorescent pigment have a particle size distribution of D90 ⁇ 5 ⁇ m.
  • the fluorescent substances used in the fluorescent pigment composition according to the present invention can be roughly classified into two groups, namely a group of fluorescent pigments that can be excited by an ultraviolet light of a wavelength of near 254 nm often used as an ultraviolet light of a relatively short wavelength (in a germicidal lamp), and a group of fluorescent substances that can be excited in a broad wavelength range of ultraviolet light inclusive of both an ultraviolet light of near 365 nm often used as an ultraviolet light of a relatively long wavelength, and an ultraviolet light of near 254 nm.
  • the first wavelength preferably is shorter than the second wavelength, and the above mentioned second fluorescent pigment emits light upon irradiation by each of the ultraviolet light of the first and second wavelengths.
  • the colors of light emitted from the first and the second fluorescent pigments are mixed to develop a color not obtained before, and hence a fluorescent luminous product conatining the inventive composition that glows in a color not obtained before can be obtained.
  • a colorless inorganic pigment prepared by calcining a composition comprising a crystal of an oxide, sulfide, silicate, phosphate, tangstate, or the like, of Ca, Ba, Mg, Zn, Cd or the like, as a principal component with a metallic element such as Mg, Ag, Cu, Sb, or Pb, or a rare-earth element such as lanthanoids, added therein as an activating agent, can be used.
  • An inorganic fluorescent substance emitting a red light includes, for example, Ln 2 O 3 :Eu; Ln 2 VO 4 :Eu; Ln(V,P)O 4 :EU; Ln 2 (V 1 P, B)O 4 ;Eu; Ln 2 VO 4 :Eu; Ln 2 (V,P)O 4 :Eu; Ln 2 (V,P,B)O 4 :Eu; Y 2 O 3 :Eu; YVO 4 :Eu; Y(V,P)O 4 :EU; Y(V,P,B)O 4 ;Eu; YVO 4 :Eu; Y(V,P)O 4 :Eu; Y(V,P)O 4 :Eu; Y(V,P,B)O 4 ;Eu; Mg 4 Ge0 5 , 5 F:Mn; SrMg(SiO 4 ) 2 :Eu,Mn; CaSnO 4 :E
  • An inorganic fluorescent substance emitting a green light includes, for example, ZnSiO 4 :Mn; (CeJb)MgAI 11 Oi 9 ; (CeJb 1 Mn)MgAI 11 O 19 ; LaPO 4 :Ce,Tb; Y 2 Si0 5 :Ce,Tb; MgGa 2 O 4 :Mn, (Ba(Eu)(Mg(Mn)AI 16 O 27 ; Zn 2 SiO 4 Jb; Y 2 O 3 :Eu; AI 2 O 3 Jb; Y 3 AI 5 O 12 Jb; SrAI 2 O 4 :Eu; and the like.
  • An inorganic fluorescent substance emitting a blue or yellow light includes, for example, Y 3 AI 5 O 12 :Ce; Y 3 (AI, Ga) 5 O 12 :Ce, both yellow emission; and Sr 3 Ca 2 (PO 4 ) 3 CI:Eu; (SrBaCa) 5 (PO 4 ) 3 CI:Eu; CaWO 4 ; CaW0 4 :Pb; Ba,MgAI 10 O 17 :Eu,Mn , BaMg 2 AI 16 O 27 )Eu, Mn; Ba, MgAI 10 O 17 :Eu; BaMg 2 AI 16 O 27 )Eu, all blue emission, and the like.
  • the particle size of the fluorescent pigments is of crucial importance for its characteristics of fluorescence such as brightness as well as the printability in case they are incorporated into - A - an ink.
  • the diameter of 90 percent of the particles (D90) is equal to or less than 5 ⁇ m, more preferably equal to or less than 3 ⁇ m, and most preferably equal to or less than 1 ⁇ m.
  • the characteristics of the ink improve as the particle size of the pigment particles therein become smaller.
  • the fluorescent pigment composition comprises equal amounts of the first and the second fluorescent pigment.
  • other mixtures wherein one of the two fluorescent pigments is present in an amount higher than 50% by weight (up to 95% by weight) are also suitable in certain circumstances.
  • a fluorescent pigment composition comprising equal amounts of either YVO4:Eu, Y(V,P)O4:Eu or Y(V,P,B)O4:Eu as the first fluorescent pigment and either BaMgAI 10 Oi 7 :Eu,Mn, BaMg 2 AI 16 O 27 )Eu, Mn, BaMgAI 10 Oi 7 :Eu, or BaMg 2 AI 16 O 27 )Eu as the second fluorescent pigment.
  • a second aspect of the present invention relates to a product containing the fluorescent pigment composition described hereinbefore for forgery prevention.
  • a product can be made that emit light of a mutually different wavelength range, that is, fluorescence of a mutually different color upon changing the excitation wavelength, by choosing at least one fluorescent substance each, from the above mentioned two groups of the fluorescent substance each excitable by a mutually different excitation wavelength.
  • the fluorescent pigment composition according to the present invention comprises two species of fluorescent pigments.
  • Each of the fluorescent pigments emits light of a mutually different wavelength range, and hence fluorescent luminous products that emit light of a color not obtained before can be obtained by observing the mixture of the colors of light emissions from the two fluorescent pigments.
  • the product for forgery prevention is based on a fluorescent luminous ink comprising the fluorescent pigment composition described hereinbefore and an ink vehicle.
  • the ink is so constituted that the first fluorescent pigment alone emits blue light by the ultraviolet light of 365 nm and both of the first and second fluorescent substances emit light by the ultraviolet light of 254 nm, apparently emitting red light which is the mixed color of the light emissions from the two fluorescent substances, an authenticity checker can judge the authenticity of a forgery prepared by a forger using a fluorescent substance that glows in a blue color upon irradiation by the ultraviolet light of 365 nm, by checking the fluorescent image using each of the two ultraviolet light of the wavelength of 365 nm and 245 nm.
  • the forgery since the forgery is prepared relying on the imitation particularly with respect to the fluorescence in response to the ultraviolet light of 365 nm, the authenticity thereof can be judged by checking whether it emits light of a red color upon irradiation by the ultraviolet light of 245 nm or not.
  • the first wavelength is preferably longer than the second wavelength, and the second fluorescent pigment does not substantially emit light by the ultraviolet light of the first wavelength.
  • an ultraviolet light of a wavelength that can excite either the first fluorescent pigment or the second fluorescent pigment and does not substantially excite the other is irradiated thereon, either one of the two fluorescent pigments alone emits light, and hence the color of light thus emitted can be made different from the color of light emitted upon irradiation by the ultraviolet light of a wavelength that can excite the other fluorescent pigment.
  • the fluorescent luminous product containing the inventive pigment composition for instance a luminous ink that emits light of a different wavelength range, namely a different color by changing the excitation wavelength can be prepared, which can help enhance the forgery prevention capability.
  • the content of the fluorescent substance in the total composition that constitutes the fluorescent luminous ink without the solvent is preferably from 15 to 80% by weight in view of enhancing both brightness and transferability (adhesivity) to the print substrate, and more preferably is from 20 to 50% by weight. If the content of the fluorescent substance is less than 15% by weight, the brightness thereof in the state of the ink composition may extremely decline depending upon the species of the fluorescent substance. The brightness of an ink composition may decline in a certain occasion to about one tenth of the inherent brightness of the fluorescent substance itself if the content thereof is, for example about 12% by weight.
  • the forgery prevention effect can be enhanced even further by incorporating a combination of plural patterns comprising fluorescent luminous inks according to the present invention in a fluorescent image formed product.
  • a fluorescent luminous ink according to the present invention comprises, as in the case of an ordinary printing ink, a fluorescent material, a vehicle, an auxiliary agent, and the like.
  • the fluorescent material herein is a fluorescent substance that glows in various colors such as red, green, and blue, and comprises two species of fluorescent pigments, each glowing in a color of a mutually different wavelength range.
  • a fluorescent luminous ink according to the present invention can be prepared by incorporating therein two species of fluorescent pigment each emitting light of a mutually different wavelength range, selected from the compounds of Ln 2 O 3 )Eu; Ln 2 VO 4 )Eu; Ln(V,P)O 4 :EU; Ln 2 (V,P,B)O 4 ;Eu; Ln 2 VO 4 :Eu; Ln 2 (V,P)O 4 :Eu; Ln 2 (V,P,B)O 4 :Eu; Y 2 O 3 :Eu; YVO 4 :Eu; Y(V,P)O 4 :EU; Y(V,P,B)O 4 ;Eu; YVO 4 :Eu; Y(V,P)O 4 :Eu; Y(V,P)O 4 :Eu; Y(V,P,B)O 4 ;Eu; Mg 4 Ge0 5 , 5 F:Mn; SrM
  • the light emitting substances are meant to be mutually different with respect to the wavelength range of fluorescence, so long as there is a wavelength range wherein either of them does not emit light.
  • the wavelength range of light emissions thereof does not overlap with each other.
  • a surface treatment to the fluorescent substance in order to improve the properties of the fluorescent substance (hiding power, coloring ability, oil absorbing ability, durability, and the like).
  • a surface treatment thereto to improve its affinity to an oleophilic polymer, since its surface is hydrophilic and hence is of a poor affinity to an oleophilic polymer.
  • Such methods for example include the following methods.
  • Coating functions as a kind of a surfactant.
  • a dispersing agent including fatty acids and fatty acid salts of a low molecular weight or a high molecular weight, a dispersing agent of wax, or the like may be used.
  • Coupling agent A coupling agent tightly bonds with a fluorescent substance and reacts with a polymer as well.
  • a silane compound, a titanium compound, a metallic chelate compound, or the like may be used.
  • Polymerizable monomer A low molecular weight monomer or oligomer is made to react with the surface of a fluorescent substance to form an irreversible layer.
  • a polymerizable organic acid, or a reactive oligomer may be used.
  • thermoplastic resin examples of which include, polyethylene based polymers [polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), vinyl chloride-vinyl acetate copolymer], polypropylene (PP), vinyl based polymers [polyvinyl chloride) (PVC), polyvinyl butyral) (PVB), polyvinyl alcohol) (PVA), poly(vinylidene chloride) (PVdC), polyvinyl acetate) (PVAc), polyvinyl formal) (PVF)], polystyrene based polymers [polystyrene (PS), styrene-acrylonitrile copolymer (AS),
  • thermosetting resins such as resol type phenolic resin, a urea resin, a melamine resin, a polyurethane resin, an epoxy resin, an unsaturated polyester and the like, and natural resins such as protein, gum, shellac, copal, starch and rosin may also be used.
  • Emulsions for use in a water-based paint include for example, a vinyl acetate (homopolymer) emulsion, a vinyl acetate-acrylic ester copolymer emulsion, a vinyl acetate-ethylene copolymer emulsion (EVA emulsion), a vinyl acetate-vinyl versatate copolymer resin emulsion, a vinyl acetate-polyvinyl alcohol copolymer resin emulsion, a vinyl acetate-vinyl chloride copolymer resin emulsion, an acrylic emulsion, an acryl silicone emulsion, a styrene- acrylate copolymer resin emulsion, a polystyrene emulsion, an urethane polymer emulsion, a polyolefin chloride emulsion, an epoxy-acrylate dis
  • a plasticizer for stabilizing the flexibility and strength of the print film and a solvent for adjusting the viscosity and drying property thereof may be added according to the needs therefor.
  • a solvent of a low boiling temperature of about 100 0 C and a petroleum solvent of a high boiling temperature of 25O 0 C or higher, may be used according to the type of the printing method.
  • An alkylbenzene or the like, for example may be used as a solvent of a low boiling temperature.
  • an auxiliary agent including a variety of reactive agents for improving drying property, viscosity, and dispersibility, may suitably be added.
  • the auxiliary agents are to adjust the performance of the ink, and for example, a compound that improves the abrasion resistance of the ink surface and a drying agent that accelerates the drying of the ink, and the like may be employed.
  • a photopolymerization-curable resin or an electron beam curable resin wherein a solvent is not used may also be employed as a binder resin that is a principal component of the vehicle.
  • the examples thereof include an acrylic resin, and specific examples of acrylic monomers commercially available are shown below.
  • a monofunctional acrylate monomer that may be used includes for example, 2-ethylhexyl acrylate, 2-ethylhexyl-EO adduct acrylate, ethoxydiethylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate-caprolactone addduct, 2- phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, nonyl phenol-EO adduct acrylate, (nonyl phenol-EO adduct)-caprolactone adduct acrylate, 2-hydroxy-3-phenoxypropyl acrylate, tetrahydrofurfuryl acrylate, furfuryl alcohol-caprolactone adduct acrylate, acryloyl morpholine, dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, is
  • a polyfunctional acrylate monomer that may be used includes hexanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol hydroxypivalate diacrylate, (neopentyl glycol hydroxypivalate)-caprolactone adduct diacrylate, (1 ,6-hexanediol diglycidyl ether)-acrylic acid adduct, (hydroxypivalaldehyde-trimethylolpropane acetal) diacrylate, 2,2-bis[4- (acryloyloxydiethoxy)phenyl]propane, 2,2-bis[4-(acryloyloxydiethoxy)phenyl]methane, hydrogenated bisphenol A-ethylene oxide adduct diacrylate, tricyclodecanedimethanol diacrylate, trimethylolpropane triacrylate, pentaerithri
  • Inks comprising the above resins are free of solvent and are so constituted as to polymerize in chain reaction upon irradiation by an electron beam or electromagnetic waves.
  • a photopolymerization initiator and depending on the needs therefor, a sensitizing agent, and auxiliary agents such as a polymerization inhibitor and a chain transfer agent, and the like may be added thereto.
  • photo-polymerization initiators there are, (1 ) an initiator of direct photolysis type including an arylalkyl ketone, an oxime ketone, an acylphosphine oxide, or the like, (2) an initiator of radical polymerization reaction type including a benzophenone derivative, a thioxanthone derivative, or the like, (3) an initiator of cationic polymerization reaction type including an aryl diazonium salt, an aryl iodinium salt, an aryl sulfonium salt, and an aryl acetophenone salt, or the like, and in addition, (4) an initiator of energy transfer type, (5) an initiator of photoredox type, (6) an initiator of electron transfer type, and the like.
  • a photopolymerization initiator is not necessary and a resin of the same type as in the case of the ultraviolet-irradiation type inks can be used, and various kinds of auxiliary agent may be added thereto according to the needs therefor.
  • a fluorescent luminous ink comprising the fluorescent pigments, a vehicle, and auxiliary agents may further comprise an erasable coloring agent having irreversibility.
  • the erasable coloring agent has an absorption band in a visible range prior to a color-erasing treatment, that is to say, is colored, which is characterized in that it irreversibly transforms itself to cease to have the absorption band, namely to become transparent to visible light upon a color-erasing treatment, for example, upon irradiation by near infrared light thereon.
  • the printed image formed thereby can be identified by the naked eye without irradiating ultraviolet light thereon, and hence the accuracy of the printing can be improved.
  • the color-erasing treatment it can be made transparent to visible light.
  • a third aspect of the present invention relates to a fluorescent image formed by at least one fluorescent luminous ink described hereinbefore.
  • the fluorescent image according to the present invention comprises at least one fluorescent image-forming layer on a substrate, which fluorescent image-forming layer comprises the first fluorescent pigment emitting light of the first wavelength in a visible light range upon irradiation by the ultraviolet light of the first wavelength and the second fluorescent pigment emitting light of the second wavelength in a visible light range being different from the above first wavelength in a visible light range upon irradiation by the ultraviolet light of the second wavelength, and is substantially transparent to visible light.
  • the fluorescent image formed product according to the present invention comprises a fluorescent image-forming layer comprising at least two species of fluorescent pigment, each of which emits light of a mutually different wavelength range.
  • a fluorescent image formed product that emits light of a color not obtained before can be obtained by observing the mixed color of light emissions from at least two species of the fluorescent substance.
  • a fluorescent image formed product that emits light of a different wavelength range, namely light of a different color upon changing the excitation wavelength can be prepared by choosing such fluorescent pigments for use therein as are excited by a mutually different excitation wavelength.
  • the above mentioned first wavelength preferably is shorter than the above mentioned second wavelength and the second fluorescent pigment emits light by each of the ultraviolet light of the first wavelength and the second wavelength.
  • the ultraviolet light of the wavelength that can excite both of the first and second fluorescent substances, a fluorescent image formed product that glows in a color not obtained before can be obtained, as a result of mixing of the colors of light emissions from the first and the second fluorescent substances.
  • the first wavelength is preferably longer than the second wavelength, and the second fluorescent substance does not substantially emit light by the ultraviolet light of the first wavelength.
  • an ultraviolet light of a wavelength that can excite either the first or the second fluorescent substances and does not substantially excite the other is irradiated, only either one of the two fluorescent substances alone emits light, and hence the color of thus emitted light can be made different from the color of light emitted upon irradiation by an ultraviolet light of a wavelength that can excite the other fluorescent substance.
  • a fluorescent image formed product that emits light of a mutually different wavelength range, namely a mutually different color upon changing the excitation wavelength, can be prepared, which can help enhance the forgery prevention capability.
  • a fluorescent image formed product according to the present invention comprising at least two fluorescent pigments can be obtained by forming a fluorescent image forming layer on a substrate using the fluorescent luminous ink by a variety of methods known in the art.
  • an anastatic printing method an intaglio printing method, a gravure printing method, a planographic printing method of offset printing type, a screen (perforated plate) printing method, a relief type printing method such as flexo or letter press printing or the like may be used.
  • a thermal transfer method or an ink jet printing method may be used as well.
  • thermoplastic resin as a binder resin, which is a principal component of the vehicle.
  • the thickness of the fluorescent image-forming layer can be suitably determined according to the required brightness of fluorescence and the required content of the fluorescent substance, which can be set for example, somewhere between 1 and 10 ⁇ m.
  • fluorescent substance particles of a relatively small particle size is employed in view of keeping the transparency as described above, and the lack of the sufficient intensity of fluorescence resulting from the small particle size in question can be compensated by increasing the thickness of the fluorescent image-forming layer.
  • a visible image-forming layer printed on an under layer, an intermediate layer, a protective layer, and the like to be employed in the practice of the present invention those known in the art can be used, so long as the fluorescent image-forming layer comprising the two species of fluorescent substances having a mutually different wavelength range of light emission on a substrate are formed by the method.
  • camouflage pattern or a back ground pattern printed on an under layer using a visible ink in the fluorescent image- forming area it is also preferable to print a camouflage pattern or a back ground pattern printed on an under layer using a visible ink in the fluorescent image- forming area. It is preferable that the camouflage pattern has as high randomness as practicable and has a faint color so as to give as little influence as practicable to the color of light emitted from the fluorescent pigments.
  • the visible image-forming layer printed on an under layer can be formed by a printing method known in the art using a color paint or ink also known in the art.
  • a color paint or ink may be prepared by adding a pigment of various species to the binder according to the intended color.
  • the binder the resins shown above as an example of the resins that constitutes the vehicle component of the fluorescent luminous ink to be used in the fluorescent image-forming layer can be employed.
  • a plasticizer, a stabilizer, a wax, a drying agent, a supplementary agent for drying, a curing agent, a thickener, a dispersing agent, a solvent, a diluent, or the like may be added according to the needs therefor.
  • the printing method that may be used includes such printing method as an ordinary gravure method, a roll method, a knife-edge method, an offset method, and the like, or a transfer printing method. In cases where a transfer printing method is used, it is preferable to smooth the surface of the receiving layer by coating a suitable resin in advance to form a smoothing layer thereon for the purpose of improving the adhesivity of the transfer pattern.
  • a resin shown above as an example of the resins that constitutes the vehicle of the fluorescent luminous ink for use in the fluorescent image-forming layer can be employed as a constituent thereof.
  • a resin of photopolymerization-curable type or electron beam curable type wherein a solvent is not used is preferable, and for example, an acrylic resin may be used, which can be prepared by using the acrylic monomer or monomers.
  • a solvent or an auxiliary component may be used according to the needs therefor.
  • the intermediate layer it is not particularly limited. However, with respect to the intermediate layer disposed below the fluorescent image-forming layer, it may be formed as an ultraviolet absorption layer wherein an ultraviolet absorber is substantially immobilized.
  • the above intermediate layer can comprise, for example at least one ultraviolet absorber and a resin, to form an ultraviolet absorbing layer.
  • the said ultraviolet absorbing layer wherein an ultraviolet absorber is substantially immobilized can be prepared by employing an ultraviolet absorber selected from the group consisting of a particulate material having ultraviolet absorbing ability or a resin having an ultraviolet absorbing functional group.
  • an ultraviolet absorbing inorganic pigment for example, zinc oxide, titanium oxide, or the like can be used.
  • the particle size of the above particles is preferably in a range of from 0.1 to 1 ⁇ m from the view point that they are substantially transparent and do not substantially migrate to the fluorescent image-forming layer.
  • An organic ultraviolet absorber that may also be used includes an ultraviolet absorber of benzophenone type, benzotriazole type, acrylate type, and salicylate type.
  • the ultraviolet absorber of benzophenone type includes for example, 2-hydroxy-4-methoxybenzophenone, 2-2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octooxybenzophenone, 2,4- dihydroxybenzophenone, resorcinol monobenzoate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4- hydroxybenzoate, 2-hydroxy-4-n-octylbenzophenone and the like.
  • the ultraviolet absorber of benzotriazloe type includes for example, 2-(2'-hydroxy-5'-methylphenyl) benzotriazole (Tinuvin P, made by Ciba Geigy AG), 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5- chlorobenzotriazole (Tinuvin 326, made by Ciba Geigy AG), 2-[2-hydroxy-3,5-bis( ⁇ , ⁇ - dimethylbenzyl)phenyl]-2H-benzotriazole (Tinuvin 234, made by Ciba Geigy AG), and the like.
  • the ultraviolet absorber of acrylate type includes for example, 2-ethylhexyl-2-cyano-3,3- diphenyl acrylate, ethyl-2-cyano-3,3-diphenyl acrylate, and the like.
  • the ultraviolet absorber of salicylate type that may be used includes for example, phenyl salicylate, 4-t-butylphenyl salicylate, p-octylphenyl salicylate, and the like.
  • the thickness of the ultraviolet absorbing layer preferably is to be determined so as to make the reflectance of the ultraviolet absorbing layer with respect to ultraviolet light substantially zero.
  • the thickness of the ultraviolet absorbing layer of no higher than 1 ⁇ m is sufficient enough and that of 0.1 to 1 ⁇ m range is suitable.
  • the ultraviolet absorbing layer may be formed on the fluorescent image-forming layer as an excitation-light shielding layer.
  • the irradiated ultraviolet light cannot reach the fluorescent image-forming layer, due to that they are absorbed by the excitation-light shielding layer, and hence light is not emitted therefrom. Consequently, by forming an area that forms the excitation-light shielding layer and another area that does not form the excitation-light shielding layer, an area that emits light and another area that does not emit light respectively can be formed, and thereby a fluorescent image can be formed.
  • the fluorescent image may be formed by forming an excitation-light shielding layer along a pattern, on top of the fluorescent image forming-layer that has been so constructed as to uniformly emit light, or may be formed by forming the excitation-light shielding layer along a different pattern, on top of the fluorescent image-forming layer that has been formed along a certain pattern.
  • the protective layer one having a high transparency to both visible light and ultraviolet light is preferred, and it can be formed by an over-laminating or over-coating method.
  • the over laminate can be formed, by laminating a transparent film of, for example, polyethylene terephthalate, polyvinyl chloride), polyethylene, polypropylene, or the like using an ordinary method.
  • the resins shown above as an example that constitutes the vehicle of the fluorescent luminous ink used in the fluorescent image-forming layer can be employed.
  • a resin of photopolymerization-curable type or electron beam curable type wherein a solvent is not used is preferable, and for example, an acrylic resin may be used, which can be prepared by using the acrylic monomer or monomers.
  • additives such as a polymerization initiator are contained therein as described above, and those additives having high transparency to visible light and ultraviolet light are to be suitably selected.
  • an OP layer may be formed using an offset printing method such as a medium process.
  • plastics such as polyvinyl chloride), nylon, cellulose diacetate, cellulose triacetate, polystyrene, polyethylene, polypropylene, polyester, polyimide, and polycarbonate, metals such as copper and aluminum, paper, impregnated paper, or the like, for example, can be used alone or in combination as a composite material.
  • the substrate can be suitably selected from the materials in view of the physical properties required thereof, for example, physical strength, rigidity, hiding power, light non-transmitting property, and the like.
  • the thickness of the substrate is normally from 0.005 to 5 mm.
  • the fluorescent whitening agent glows in blue color upon irradiation of ultraviolet light using a black light. Consequently, upon irradiation of ultraviolet light for the purpose of identifying by sight the fluorescent image formed by the fluorescent substance contained in the fluorescent image-forming layer formed on the paper substrate, the fluorescent whitening agent contained in the paper substrate also emits light as well, which causes a problem that the detection of the image becomes difficult.
  • a paper substrate that contains no, or least possible fluorescent whitening agent.
  • an ultraviolet absorbing layer that contains for example, 10% of Tinuvin ® (made by Ciba Specialty Chemicals Inc.) therein, printed on an under layer to suppress the influence of the fluorescent whitening agent, on the paper substrate.
  • a variety of light sources emitting a specific wavelength of ultraviolet light can be chosen according to the species of the fluorescent substance described above.
  • a small sized black light emitting the ultraviolet light of the wavelength of 365 nm is commercially available and can be used without difficulty.
  • a germicidal lamp emitting the ultraviolet light of the wavelength of 254 nm may be used as well. Namely, it is preferable to choose fluorescent substances based on the above two wavelength ranges, due to that it makes the practice of the present invention easier.
  • Suitable fluorescent pigments can be broadly classified into two groups, namely one that emits light upon irradiation by ultraviolet light of 254 nm but does not emit light upon irradiation by ultraviolet light of 365 nm, and the other that emits light upon irradiation by ultraviolet light of each of 254 nm and 365 nm.
  • the fluorescent image-forming layer according to the present invention comprises two species of fluorescent pigments, each emitting light of a mutually different wavelength range.
  • a fluorescent image forming layer that develops a fluorescent image glowing in two different colors in response to the wavelength of ultraviolet light irradiated thereon, for example, a fluorescent image of one color upon irradiation of the ultraviolet light of 254 nm and that of another color upon irradiation of the ultraviolet light of 365 nm, can be formed.
  • Yet another aspect of the present invention relates to a method for counterfeit-proof marking of documents as originals in a variety of ways.
  • identification papers, passports, banknotes, cheques and share certificates can be marked as being originals.
  • the method according to the invention can equally be used for creating counterfeit-proof product identification labels.
  • the economic damage caused to the global economy by product piracy and counterfeit goods is immense. It is necessary particularly to prevent counterfeiting in the case of pharmaceutical products.
  • the method according to the invention allows, for example, the counterfeit-proof marking of blister packs, so that it is possible to have a decisive effect in preventing inferior preparations being passed off as the original articles.
  • an indicator strip comprising the inventive binary fluorescent pigment composition that is not visible under normal circumstances could be applied to a suitable substrate of a product or document to be protected against counterfeiting.
  • Checking the authenticity of the article could then be effected very simply by irradiation (e.g. with a lamp that emits light of a suitable wavelength), so that the indicator strip would be visible to an observer or, in the event of a counterfeit, not visible to the observer.
  • the authenticity of branded products could also be checked in this way. It might be possible for the reproduction of a mark on packaging to be so changed under the action of light of a certain intensity and/or a certain wavelength spectrum that a consumer would be in no doubt as to the origin of the goods. Limits will thus be set on brand and/or product piracy.
  • Fluorescent luminous inks 1-1 and I-2 were prepared, wherein in
  • Y(V,P)O 4 Eu type fluorescent pigment that emits light of a red color
  • BaMg 2 AI 16 O 27 Eu,Mn type fluorescent pigment that emits light of a green color
  • Both 1-1 and I-2 contain the two fluorescent pigments in a ratio of 50:50.
  • the final printing ink formulation comprises 4% 1-1 (or I-2) fluorescent pigment powder, and 96% Vinyl/ketone clear varnish.
  • the varnish formulation is a vinyl/ketone clear varnish of 14%Vinylite VYHH (vinyl coploymer resin), 10% Ethoxypropanol and 76% Methylethylketone.
  • Fluorescent pigment powders were first incorporated into the varnish by a pre-dispersing step in that a clear varnisch is prepared, then the fluorescent pigment powder is slowly added while stirring, followed by an additional stirring of 5 min at 15 m/s. The final dispersion was obtained in a Skandex apparatus using 2 mm glass beads for 30 min. The resulting ink was then printed with a conventional cylinder (0.35 g/m 2 1-1 or I-2) on contrast paper to obtain a full shade rotogravure printing.
  • Fluorescence spectra of the light emissions from the fluorescent luminous ink 1-1 show that BaMgAI 10 Oi 7 :Eu,Mn type fluorescent pigment emits light of a blue color and the Y(V 1 P)O 4 )Eu type fluorescent pigment emits light of a red color.
  • fluorescence spectra of the light emissions from the fluorescent luminous ink 1-2 show that BaMg 2 AI 16 C ⁇ Eu 1 Mn type fluorescent pigment emits light of a blue color and the Y(V,P)O 4 :Eu type fluorescent pigment emits light of a red color.
  • the fluorescent luminous ink and the respective fluorescent image comprise two species of fluorescent pigments, each of which emits light of a mutually different wavelength range, they are able to glow in a color not obtained before, and further can be caused to emit light of a different wavelength range, namely a different color upon changing the excitation wavelength, by choosing the species of fluorescent pigments excitable by a mutually different excitation wavelength.
  • the security levels of printed matters requiring forgery prevention such as securities including a coupon and a prepaid card can be enhanced by judging the authenticity of the fluorescent luminous ink and the respective fluorescent image which have been so constituted as to emit light of different colors upon irradiating ultraviolet light of a mutually different wavelength, by irradiating thereon a plurality of ultraviolet light of a mutually different wavelength that can cause them to change the color of the emitting light.
  • a fluorescent luminous ink that emits light of a color not obtained before can be provided by incorporating therein two different fluorescent pigments each emitting light of a mutually different wavelength range. By choosing excitation wavelengths that can excite both of the two fluorescent pigments, the ink can be made to emit light of mutually different color, one upon irradiation by an ultraviolet light of the first wavelength, and the other upon irradiation by an ultraviolet light of the second wavelength.

Abstract

The present invention relates to binary fluorescent pigment compositions, products containing them and their use for forgery and counterfeit prevention. Especially, the invention relates to a luminous ink comprising two fluorescent pigments that emit light upon irradiation by ultraviolet light and an ink vehicle, wherein the first fluorescent pigment emits light of a first wavelength in a visible light range upon irradiation by an ultraviolet light of a first wavelength and is substantially transparent to visible light, and the second fluorescent substance that emits light of a second wavelength in a visible light range being different from the first wavelength in a visible light range upon irradiation by an ultraviolet light of a second wavelength and is substantially transparent to visible light. The fluorescent luminous ink is difficult to identify by sight in the presence of visible light and becomes identifiable by sight by emitting light in a visible light range upon irradiation by ultraviolet light.

Description

Binary fluorescent pigment composition and its use for forgery and counterfeit prevention
The present invention relates to binary fluorescent pigment compositions, products containing them and their use for forgery and counterfeit prevention. Especially, the invention relates to a luminous ink comprising two fluorescent pigments that emit light upon irradiation by ultraviolet light and an ink vehicle, wherein the first fluorescent pigment emits light of a first wavelength in a visible light range upon irradiation by an ultraviolet light of a first wavelength and is substantially transparent to visible light, and the second fluorescent substance that emits light of a second wavelength in a visible light range being different from the first wavelength in a visible light range upon irradiation by an ultraviolet light of a second wavelength and is substantially transparent to visible light. The fluorescent luminous ink is difficult to identify by sight in the presence of visible light and becomes identifiable by sight by emitting light in a visible light range upon irradiation by ultraviolet light.
US5005873 relates to an article comprising a substrate having markings which are provided by at least two fluorescent materials which have different excitation spectra in the ultraviolet region of the spectrum and different emission spectra in the visible region of the spectrum. US5005873 also provides a method of marking an article for identification. While inorganic phosphors are mentioned as examples of fluorescent materials, US5005873 fails to disclose their particle sizes.
US2004251833 relates to a plasma display apparatus, and more particularly to fluorescent material coated onto a fluorescent layer which is a part of the plasma display apparatus. The fluorescent material is coated on sidewalls of the partition walls and an exposed surface of an dielectric layer. The fluorescent material converts ultra-violet rays generated by discharges, into visible lights. For instance, red, green and blue (RGB) fluorescent materials are coated every three cells, ensuring displaying color images.
US2002063301 discloses a semiconductor light-emitting device constituted by mounting a semiconductor light-emitting element on a base substance, wherein the semiconductor light- emitting element has outgoing light having an emission wavelength of 390 to 420 nm; and there is included a fluorescent substance that is excited by outgoing light from the semiconductor light-emitting element and emits red light having an emission wavelength with its main emission peak in a wavelength range of 600 to 670 nm. Examples of fluorescent substances are M2O2S: Eu (M is any one or more elements selected from La, Gd and Y); 0.5MgF2 3.5MgO GeO2: Mn; Y2O3: Eu, Y(P, V)O4: Eu; etc. WO2006072919 discloses an illumination system comprising a radiation source and luminescent material comprising a phosphor of general formula (Bai.χSrx)1-aMg3- bAI14O25:EUaMnb! wherein 0<x<1 , 0<a<0.2, 0<b< 0.2, a + b > 0.
Recently in a printed matter requiring forgery prevention including securities such as a coupon and a prepaid card, a micro letter, a copy restraining pattern, an infrared absorbing ink, fluorescent luminous ink, or the like has been used for the purpose of enhancing the security level thereof. Among them, fluorescent luminous ink is ink that is hardly identifiable by the naked eye in the presence of ordinary visible light but becomes visible to the naked eye upon irradiation by ultraviolet light or infrared light, making it possible to detect the image by sight. The technology has been well known in the art.
Since anyone can easily confirm the presence or the absence of a fluorescent luminous substance used for instance in the printed matters which require forgery prevention, there is a problem that the security level of a product wherein a fluorescent substance, for instance an ink is used has been declining.
Therefore, it is an object of the present invention to provide a fluorescent pigment composition and security products containing them with an enhanced security level that is difficult to acquire.
A first aspect of the present invention relates to a pigment composition comprising a first and a second inorganic fluorescent pigment that emit light upon irradiation by ultraviolet light, wherein the first fluorescent pigment emits light of a first wavelength in a visible light range upon irradiation by an ultraviolet light of a first wavelength and is substantially transparent to visible light, and the second fluorescent pigment that emits light of a second wavelength in a visible light range that is different from the first wavelength in a visible light range upon irradiation by an ultraviolet light of a second wavelength and is substantially transparent to visible light and wherein the first and the second inorganic fluorescent pigment have a particle size distribution of D90 < 5μm.
The fluorescent substances used in the fluorescent pigment composition according to the present invention can be roughly classified into two groups, namely a group of fluorescent pigments that can be excited by an ultraviolet light of a wavelength of near 254 nm often used as an ultraviolet light of a relatively short wavelength (in a germicidal lamp), and a group of fluorescent substances that can be excited in a broad wavelength range of ultraviolet light inclusive of both an ultraviolet light of near 365 nm often used as an ultraviolet light of a relatively long wavelength, and an ultraviolet light of near 254 nm.
With respect to the fluorescent pigment composition according to the present invention, the first wavelength preferably is shorter than the second wavelength, and the above mentioned second fluorescent pigment emits light upon irradiation by each of the ultraviolet light of the first and second wavelengths. Upon irradiation by ultraviolet light of wavelengths that can excite both of the first and second fluorescent pigment, the colors of light emitted from the first and the second fluorescent pigments are mixed to develop a color not obtained before, and hence a fluorescent luminous product conatining the inventive composition that glows in a color not obtained before can be obtained.
With respect to the first and the second fluorescent pigment, a colorless inorganic pigment prepared by calcining a composition comprising a crystal of an oxide, sulfide, silicate, phosphate, tangstate, or the like, of Ca, Ba, Mg, Zn, Cd or the like, as a principal component with a metallic element such as Mg, Ag, Cu, Sb, or Pb, or a rare-earth element such as lanthanoids, added therein as an activating agent, can be used.
An inorganic fluorescent substance emitting a red light that may be used includes, for example, Ln2O3:Eu; Ln2VO4:Eu; Ln(V,P)O4:EU; Ln2(V1P, B)O4;Eu; Ln2VO4:Eu; Ln2(V,P)O4:Eu; Ln2(V,P,B)O4:Eu; Y2O3:Eu; YVO4:Eu; Y(V,P)O4:EU; Y(V,P,B)O4;Eu; YVO4:Eu; Y(V,P)O4:Eu; Y(V,P,B)O4;Eu; Mg4Ge05,5F:Mn; SrMg(SiO4)2:Eu,Mn; CaSnO4:Eu; Mg4(Ge,Sn)O5,5:Mn; Y2O3 Eu; Ln2O3 Eu (Ln=Lanthanide); Gd(Zn, Mg)B5Oi0:Ce, Mn; (Y1Eu)W3O12 and the like.
An inorganic fluorescent substance emitting a green light that may be used includes, for example, ZnSiO4:Mn; (CeJb)MgAI11Oi9; (CeJb1Mn)MgAI11O19; LaPO4:Ce,Tb; Y2Si05:Ce,Tb; MgGa2O4:Mn, (Ba(Eu)(Mg(Mn)AI16O27; Zn2SiO4Jb; Y2O3:Eu; AI2O3Jb; Y3AI5O12Jb; SrAI2O4:Eu; and the like.
An inorganic fluorescent substance emitting a blue or yellow light that may be used includes, for example, Y3AI5O12:Ce; Y3(AI, Ga)5O12:Ce, both yellow emission; and Sr3Ca2(PO4)3CI:Eu; (SrBaCa)5(PO4)3CI:Eu; CaWO4; CaW04:Pb; Ba,MgAI10O17:Eu,Mn, BaMg2AI16O27)Eu, Mn; Ba, MgAI10O17:Eu; BaMg2AI16O27)Eu, all blue emission, and the like.
The particle size of the fluorescent pigments is of crucial importance for its characteristics of fluorescence such as brightness as well as the printability in case they are incorporated into - A - an ink. With respect to the fluorescent pigment particles to be used, the diameter of 90 percent of the particles (D90) is equal to or less than 5 μm, more preferably equal to or less than 3 μm, and most preferably equal to or less than 1 μm. In case the fluorescent pigment particles are incorporated into an ink, the characteristics of the ink improve as the particle size of the pigment particles therein become smaller.
It is a general believe that the brightness of the fluorescence conversely declines to a remarkable degree when the particle size of the fluorescent substance particles becomes less than 3 μm, in particular less than 1 μm due to the application of conventional milling techniques. Surprisingly, the present inventors have shown that the use of fluorescent pigment particles wherein 90 percent of the particles have a diameter of equal to or less than 3 μm, in particluar equal to or less than 1 μm provide for an improved fluorescence in contrast to the general believe.
Preferably, the fluorescent pigment composition comprises equal amounts of the first and the second fluorescent pigment. However, other mixtures wherein one of the two fluorescent pigments is present in an amount higher than 50% by weight (up to 95% by weight) are also suitable in certain circumstances.
Especially preferred is a fluorescent pigment composition comprising equal amounts of either YVO4:Eu, Y(V,P)O4:Eu or Y(V,P,B)O4:Eu as the first fluorescent pigment and either BaMgAI10Oi7:Eu,Mn, BaMg2AI16O27)Eu, Mn, BaMgAI10Oi7:Eu, or BaMg2AI16O27)Eu as the second fluorescent pigment.
A second aspect of the present invention relates to a product containing the fluorescent pigment composition described hereinbefore for forgery prevention. Starting from said pigment composition, a product can be made that emit light of a mutually different wavelength range, that is, fluorescence of a mutually different color upon changing the excitation wavelength, by choosing at least one fluorescent substance each, from the above mentioned two groups of the fluorescent substance each excitable by a mutually different excitation wavelength.
The fluorescent pigment composition according to the present invention comprises two species of fluorescent pigments. Each of the fluorescent pigments emits light of a mutually different wavelength range, and hence fluorescent luminous products that emit light of a color not obtained before can be obtained by observing the mixture of the colors of light emissions from the two fluorescent pigments.
Preferably, the product for forgery prevention is based on a fluorescent luminous ink comprising the fluorescent pigment composition described hereinbefore and an ink vehicle.
More preferably, the ink is so constituted that the first fluorescent pigment alone emits blue light by the ultraviolet light of 365 nm and both of the first and second fluorescent substances emit light by the ultraviolet light of 254 nm, apparently emitting red light which is the mixed color of the light emissions from the two fluorescent substances, an authenticity checker can judge the authenticity of a forgery prepared by a forger using a fluorescent substance that glows in a blue color upon irradiation by the ultraviolet light of 365 nm, by checking the fluorescent image using each of the two ultraviolet light of the wavelength of 365 nm and 245 nm. In the case, since the forgery is prepared relying on the imitation particularly with respect to the fluorescence in response to the ultraviolet light of 365 nm, the authenticity thereof can be judged by checking whether it emits light of a red color upon irradiation by the ultraviolet light of 245 nm or not.
Although an effect similar to the one may be achieved by superimposing two fluorescent luminous inks each comprising the respective species of the fluorescent pigment, it is extremely difficult to imitate the above effect due to the fact that it is extremely difficult to carry out a precise superimposition and that the intensity of the emission from the fluorescent pigment in the lower layer of the superimposed fluorescent image-forming layers tends to decline causing itself to appear as a different color. Consequently, forgery by a third party is difficult and the security level can be enhanced.
With respect to the fluorescent pigment composition according to the present invention, the first wavelength is preferably longer than the second wavelength, and the second fluorescent pigment does not substantially emit light by the ultraviolet light of the first wavelength. In cases where an ultraviolet light of a wavelength that can excite either the first fluorescent pigment or the second fluorescent pigment and does not substantially excite the other is irradiated thereon, either one of the two fluorescent pigments alone emits light, and hence the color of light thus emitted can be made different from the color of light emitted upon irradiation by the ultraviolet light of a wavelength that can excite the other fluorescent pigment. As explained above, the fluorescent luminous product containing the inventive pigment composition, for instance a luminous ink that emits light of a different wavelength range, namely a different color by changing the excitation wavelength can be prepared, which can help enhance the forgery prevention capability.
Further in addition, it is possible to alter the color of fluorescence by changing the blend ratio of the two fluorescent pigments each emitting light of a mutually different wavelength range, and it is also possible, by using only two species of fluorescent pigments, to cause them to emit a plurality of light of a mutually different color. By combining these inks each emitting a plurality of light of a mutually different color, forgery by means of superimposition can be made extremely difficult.
The content of the fluorescent substance in the total composition that constitutes the fluorescent luminous ink without the solvent, is preferably from 15 to 80% by weight in view of enhancing both brightness and transferability (adhesivity) to the print substrate, and more preferably is from 20 to 50% by weight. If the content of the fluorescent substance is less than 15% by weight, the brightness thereof in the state of the ink composition may extremely decline depending upon the species of the fluorescent substance. The brightness of an ink composition may decline in a certain occasion to about one tenth of the inherent brightness of the fluorescent substance itself if the content thereof is, for example about 12% by weight.
In addition, the forgery prevention effect can be enhanced even further by incorporating a combination of plural patterns comprising fluorescent luminous inks according to the present invention in a fluorescent image formed product.
A fluorescent luminous ink according to the present invention comprises, as in the case of an ordinary printing ink, a fluorescent material, a vehicle, an auxiliary agent, and the like. The fluorescent material herein is a fluorescent substance that glows in various colors such as red, green, and blue, and comprises two species of fluorescent pigments, each glowing in a color of a mutually different wavelength range.
A fluorescent luminous ink according to the present invention can be prepared by incorporating therein two species of fluorescent pigment each emitting light of a mutually different wavelength range, selected from the compounds of Ln2O3)Eu; Ln2VO4)Eu; Ln(V,P)O4:EU; Ln2(V,P,B)O4;Eu; Ln2VO4:Eu; Ln2(V,P)O4:Eu; Ln2(V,P,B)O4:Eu; Y2O3:Eu; YVO4:Eu; Y(V,P)O4:EU; Y(V,P,B)O4;Eu; YVO4:Eu; Y(V,P)O4:Eu; Y(V,P,B)O4;Eu; Mg4Ge05,5F:Mn; SrMg(SiO4)2:Eu,Mn; CaSnO4:Eu; Mg4(Ge,Sn)O5,5:Mn; Y2O3 Eu; Ln2O3 Eu (Ln=Lanthanide), Gd(Zn, Mg)B5Oi0:Ce,Mn; (Y1Eu)W3O12; ZnSiO4:Mn; (Ce1Tb)MgAI11Oi9; (CeJb1Mn)MgAI11Oi9; LaPO4)CeJb; Y2SiO5)CeJb; MgGa2O4)Mn; (Ba(Eu)(Mg(Mn)AI16O27; Zn2SiO4Jb; Y2O3; AI2O3Jb; Y3AI5O12Jb; SrAI2O4:Eu; Y3AI5O12:Ce; Y3(AI,Ga)5O12:Ce; Sr3Ca2(PO4)3CI:Eu; (SrBaCa)5(PO4)3CI:Eu; CaWO4; CaW04:Pb; Ba1MgAI10O17)Eu1Mn; BaMg2AI16O27)Eu1Mn; Ba1MgAI10O17)Eu; BaMg2AI16O27)Eu1 and the like. Although three or more species thereof may be incorporated, it is necessary to incorporate therein at least two fluorescent pigments emitting light of a mutually different wavelength range. In this instance, the light emitting substances are meant to be mutually different with respect to the wavelength range of fluorescence, so long as there is a wavelength range wherein either of them does not emit light. However it is preferable that the wavelength range of light emissions thereof does not overlap with each other.
It is further preferable to apply a surface treatment to the fluorescent substance in order to improve the properties of the fluorescent substance (hiding power, coloring ability, oil absorbing ability, durability, and the like). Particularly in case wherein an inorganic fluorescent substance is used, it is preferable to apply a surface treatment thereto to improve its affinity to an oleophilic polymer, since its surface is hydrophilic and hence is of a poor affinity to an oleophilic polymer. Such methods for example include the following methods.
(a) Coating: Coating functions as a kind of a surfactant. For example, a dispersing agent including fatty acids and fatty acid salts of a low molecular weight or a high molecular weight, a dispersing agent of wax, or the like may be used.
(b) Coupling agent: A coupling agent tightly bonds with a fluorescent substance and reacts with a polymer as well. For example a silane compound, a titanium compound, a metallic chelate compound, or the like, may be used.
(c) Polymerizable monomer: A low molecular weight monomer or oligomer is made to react with the surface of a fluorescent substance to form an irreversible layer. For example, a polymerizable organic acid, or a reactive oligomer may be used.
With respect to the vehicle of the fluorescent luminous ink according to the present invention, one that does not substantially have an absorption band in the wavelength range of ultraviolet light that excite the fluorescent substance and in the wavelength range of visible light is preferred. With respect to the binder resin which is a principal constituent of the vehicle, a thermoplastic resin may be used, examples of which include, polyethylene based polymers [polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), vinyl chloride-vinyl acetate copolymer], polypropylene (PP), vinyl based polymers [polyvinyl chloride) (PVC), polyvinyl butyral) (PVB), polyvinyl alcohol) (PVA), poly(vinylidene chloride) (PVdC), polyvinyl acetate) (PVAc), polyvinyl formal) (PVF)], polystyrene based polymers [polystyrene (PS), styrene-acrylonitrile copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS)], acrylic based polymers [poly(methyl methacrylate) (PMMA), MMA-styrene copolymer], polycarbonate (PC), celluloses [ethyl cellulose (EC), cellulose acetate (CA), propyl cellulose (CP), cellulose acetate butyrate (CAB), cellulose nitrate (CN)], fluorin based polymers [polychlorofluoroethylene (PCTFE), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer (FEP), poly(vinylidene fluoride) (PVdF)], urethane based polymers (PU), nylons [type 6, type 66, type 610, type 11], polyesters (alkyl) [polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexane terephthalate (PCT)], novolac type phenolic resins, or the like. In addition, thermosetting resins such as resol type phenolic resin, a urea resin, a melamine resin, a polyurethane resin, an epoxy resin, an unsaturated polyester and the like, and natural resins such as protein, gum, shellac, copal, starch and rosin may also be used.
Further, the above resins may be in an emulsion form for use in a water-based paint. Emulsions for use in a water-based paint include for example, a vinyl acetate (homopolymer) emulsion, a vinyl acetate-acrylic ester copolymer emulsion, a vinyl acetate-ethylene copolymer emulsion (EVA emulsion), a vinyl acetate-vinyl versatate copolymer resin emulsion, a vinyl acetate-polyvinyl alcohol copolymer resin emulsion, a vinyl acetate-vinyl chloride copolymer resin emulsion, an acrylic emulsion, an acryl silicone emulsion, a styrene- acrylate copolymer resin emulsion, a polystyrene emulsion, an urethane polymer emulsion, a polyolefin chloride emulsion, an epoxy-acrylate dispersion, an SBR latex, and the like.
Furthermore, to the vehicle, a plasticizer for stabilizing the flexibility and strength of the print film and a solvent for adjusting the viscosity and drying property thereof may be added according to the needs therefor. A solvent of a low boiling temperature of about 1000C and a petroleum solvent of a high boiling temperature of 25O0C or higher, may be used according to the type of the printing method. An alkylbenzene or the like, for example may be used as a solvent of a low boiling temperature.
Further in addition, an auxiliary agent including a variety of reactive agents for improving drying property, viscosity, and dispersibility, may suitably be added. The auxiliary agents are to adjust the performance of the ink, and for example, a compound that improves the abrasion resistance of the ink surface and a drying agent that accelerates the drying of the ink, and the like may be employed.
A photopolymerization-curable resin or an electron beam curable resin wherein a solvent is not used may also be employed as a binder resin that is a principal component of the vehicle. The examples thereof include an acrylic resin, and specific examples of acrylic monomers commercially available are shown below.
A monofunctional acrylate monomer that may be used includes for example, 2-ethylhexyl acrylate, 2-ethylhexyl-EO adduct acrylate, ethoxydiethylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate-caprolactone addduct, 2- phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, nonyl phenol-EO adduct acrylate, (nonyl phenol-EO adduct)-caprolactone adduct acrylate, 2-hydroxy-3-phenoxypropyl acrylate, tetrahydrofurfuryl acrylate, furfuryl alcohol-caprolactone adduct acrylate, acryloyl morpholine, dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, isobornyl acrylate, (4,4-dimethyl-1 ,3-dioxane)-caprolactone adduct acrylate, (3- methyl-5,5-dimethyl-1 ,3-dioxane)-caprolactone adduct acrylate, and the like.
A polyfunctional acrylate monomer that may be used includes hexanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol hydroxypivalate diacrylate, (neopentyl glycol hydroxypivalate)-caprolactone adduct diacrylate, (1 ,6-hexanediol diglycidyl ether)-acrylic acid adduct, (hydroxypivalaldehyde-trimethylolpropane acetal) diacrylate, 2,2-bis[4- (acryloyloxydiethoxy)phenyl]propane, 2,2-bis[4-(acryloyloxydiethoxy)phenyl]methane, hydrogenated bisphenol A-ethylene oxide adduct diacrylate, tricyclodecanedimethanol diacrylate, trimethylolpropane triacrylate, pentaerithritol triacrylate, (trimethylolpropane- propylene oxide) adduct triacrylate, glycerine-propylene oxide adduct triacrylate, a mixture of dipentaerithritol hexaacrylate and pentaacrylate, esters of dipentaerithritol and lower fatty acid and acrylic acid, dipentaerithritol-caprolactone adduct acrylate, tris(acryloyloxyethyl) isocyanurate, 2-acryloyloxyethyl phosphate, and the like.
Inks comprising the above resins are free of solvent and are so constituted as to polymerize in chain reaction upon irradiation by an electron beam or electromagnetic waves. With respect to inks of ultraviolet-irradiation type among these inks, a photopolymerization initiator, and depending on the needs therefor, a sensitizing agent, and auxiliary agents such as a polymerization inhibitor and a chain transfer agent, and the like may be added thereto.
With respect to photo-polymerization initiators, there are, (1 ) an initiator of direct photolysis type including an arylalkyl ketone, an oxime ketone, an acylphosphine oxide, or the like, (2) an initiator of radical polymerization reaction type including a benzophenone derivative, a thioxanthone derivative, or the like, (3) an initiator of cationic polymerization reaction type including an aryl diazonium salt, an aryl iodinium salt, an aryl sulfonium salt, and an aryl acetophenone salt, or the like, and in addition, (4) an initiator of energy transfer type, (5) an initiator of photoredox type, (6) an initiator of electron transfer type, and the like. With respect to the inks of electron beam-curable type, a photopolymerization initiator is not necessary and a resin of the same type as in the case of the ultraviolet-irradiation type inks can be used, and various kinds of auxiliary agent may be added thereto according to the needs therefor.
A fluorescent luminous ink comprising the fluorescent pigments, a vehicle, and auxiliary agents may further comprise an erasable coloring agent having irreversibility. In this case, the erasable coloring agent has an absorption band in a visible range prior to a color-erasing treatment, that is to say, is colored, which is characterized in that it irreversibly transforms itself to cease to have the absorption band, namely to become transparent to visible light upon a color-erasing treatment, for example, upon irradiation by near infrared light thereon. In cases where the printing is carried out using a fluorescent luminous ink comprising such an erasable coloring agent as, the printed image formed thereby can be identified by the naked eye without irradiating ultraviolet light thereon, and hence the accuracy of the printing can be improved. By subsequently carrying out the color-erasing treatment, it can be made transparent to visible light.
A third aspect of the present invention relates to a fluorescent image formed by at least one fluorescent luminous ink described hereinbefore. The fluorescent image according to the present invention comprises at least one fluorescent image-forming layer on a substrate, which fluorescent image-forming layer comprises the first fluorescent pigment emitting light of the first wavelength in a visible light range upon irradiation by the ultraviolet light of the first wavelength and the second fluorescent pigment emitting light of the second wavelength in a visible light range being different from the above first wavelength in a visible light range upon irradiation by the ultraviolet light of the second wavelength, and is substantially transparent to visible light.
The fluorescent image formed product according to the present invention comprises a fluorescent image-forming layer comprising at least two species of fluorescent pigment, each of which emits light of a mutually different wavelength range. Hence a fluorescent image formed product that emits light of a color not obtained before can be obtained by observing the mixed color of light emissions from at least two species of the fluorescent substance. Further, a fluorescent image formed product that emits light of a different wavelength range, namely light of a different color upon changing the excitation wavelength, can be prepared by choosing such fluorescent pigments for use therein as are excited by a mutually different excitation wavelength.
With respect to the fluorescent image formed product according to the present invention, the above mentioned first wavelength preferably is shorter than the above mentioned second wavelength and the second fluorescent pigment emits light by each of the ultraviolet light of the first wavelength and the second wavelength. Upon irradiation by the ultraviolet light of the wavelength that can excite both of the first and second fluorescent substances, a fluorescent image formed product that glows in a color not obtained before can be obtained, as a result of mixing of the colors of light emissions from the first and the second fluorescent substances.
With respect to the fluorescent image formed product according to the present invention, the first wavelength is preferably longer than the second wavelength, and the second fluorescent substance does not substantially emit light by the ultraviolet light of the first wavelength. In cases where an ultraviolet light of a wavelength that can excite either the first or the second fluorescent substances and does not substantially excite the other is irradiated, only either one of the two fluorescent substances alone emits light, and hence the color of thus emitted light can be made different from the color of light emitted upon irradiation by an ultraviolet light of a wavelength that can excite the other fluorescent substance. Thus, a fluorescent image formed product that emits light of a mutually different wavelength range, namely a mutually different color upon changing the excitation wavelength, can be prepared, which can help enhance the forgery prevention capability.
A fluorescent image formed product according to the present invention comprising at least two fluorescent pigments can be obtained by forming a fluorescent image forming layer on a substrate using the fluorescent luminous ink by a variety of methods known in the art. For example, an anastatic printing method, an intaglio printing method, a gravure printing method, a planographic printing method of offset printing type, a screen (perforated plate) printing method, a relief type printing method such as flexo or letter press printing or the like may be used. In addition, a thermal transfer method or an ink jet printing method may be used as well. In case of using a thermal transfer method, it is preferable to maintain enough amount of light by keeping the thickness of the fluorescent image-forming layer at least equal to or higher than 6 μm, and hence it is preferable to add a binder or a wax such as carbana wax to the image-forming layer. Since it is preferable to thermally melt the surface of the ink, it is preferable to use a thermoplastic resin as a binder resin, which is a principal component of the vehicle.
The thickness of the fluorescent image-forming layer can be suitably determined according to the required brightness of fluorescence and the required content of the fluorescent substance, which can be set for example, somewhere between 1 and 10 μm. According to the present invention, fluorescent substance particles of a relatively small particle size is employed in view of keeping the transparency as described above, and the lack of the sufficient intensity of fluorescence resulting from the small particle size in question can be compensated by increasing the thickness of the fluorescent image-forming layer.
With respect to a substrate, a visible image-forming layer printed on an under layer, an intermediate layer, a protective layer, and the like to be employed in the practice of the present invention, those known in the art can be used, so long as the fluorescent image- forming layer comprising the two species of fluorescent substances having a mutually different wavelength range of light emission on a substrate are formed by the method.
In order to make identification by sight of the image formed as a fluorescent image more difficult in the presence of visible light, it is also preferable to print a camouflage pattern or a back ground pattern printed on an under layer using a visible ink in the fluorescent image- forming area. It is preferable that the camouflage pattern has as high randomness as practicable and has a faint color so as to give as little influence as practicable to the color of light emitted from the fluorescent pigments.
The visible image-forming layer printed on an under layer can be formed by a printing method known in the art using a color paint or ink also known in the art. For example, a color paint or ink may be prepared by adding a pigment of various species to the binder according to the intended color. As for the binder, the resins shown above as an example of the resins that constitutes the vehicle component of the fluorescent luminous ink to be used in the fluorescent image-forming layer can be employed. Further, to the color paint or ink, a plasticizer, a stabilizer, a wax, a drying agent, a supplementary agent for drying, a curing agent, a thickener, a dispersing agent, a solvent, a diluent, or the like may be added according to the needs therefor. The printing method that may be used includes such printing method as an ordinary gravure method, a roll method, a knife-edge method, an offset method, and the like, or a transfer printing method. In cases where a transfer printing method is used, it is preferable to smooth the surface of the receiving layer by coating a suitable resin in advance to form a smoothing layer thereon for the purpose of improving the adhesivity of the transfer pattern.
With respect to the intermediate layer, one having high transparency to visible light is preferable. A resin shown above as an example of the resins that constitutes the vehicle of the fluorescent luminous ink for use in the fluorescent image-forming layer can be employed as a constituent thereof. In particular, a resin of photopolymerization-curable type or electron beam curable type wherein a solvent is not used is preferable, and for example, an acrylic resin may be used, which can be prepared by using the acrylic monomer or monomers. In addition, a solvent or an auxiliary component may be used according to the needs therefor.
With respect to the intermediate layer, it is not particularly limited. However, with respect to the intermediate layer disposed below the fluorescent image-forming layer, it may be formed as an ultraviolet absorption layer wherein an ultraviolet absorber is substantially immobilized. The above intermediate layer can comprise, for example at least one ultraviolet absorber and a resin, to form an ultraviolet absorbing layer. The said ultraviolet absorbing layer wherein an ultraviolet absorber is substantially immobilized can be prepared by employing an ultraviolet absorber selected from the group consisting of a particulate material having ultraviolet absorbing ability or a resin having an ultraviolet absorbing functional group.
As for the particulate material having ultraviolet absorbing ability, an ultraviolet absorbing inorganic pigment for example, can be used. For example, zinc oxide, titanium oxide, or the like can be used. The particle size of the above particles is preferably in a range of from 0.1 to 1 μm from the view point that they are substantially transparent and do not substantially migrate to the fluorescent image-forming layer. An organic ultraviolet absorber that may also be used includes an ultraviolet absorber of benzophenone type, benzotriazole type, acrylate type, and salicylate type. The ultraviolet absorber of benzophenone type includes for example, 2-hydroxy-4-methoxybenzophenone, 2-2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octooxybenzophenone, 2,4- dihydroxybenzophenone, resorcinol monobenzoate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4- hydroxybenzoate, 2-hydroxy-4-n-octylbenzophenone and the like. The ultraviolet absorber of benzotriazloe type includes for example, 2-(2'-hydroxy-5'-methylphenyl) benzotriazole (Tinuvin P, made by Ciba Geigy AG), 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5- chlorobenzotriazole (Tinuvin 326, made by Ciba Geigy AG), 2-[2-hydroxy-3,5-bis(α,α- dimethylbenzyl)phenyl]-2H-benzotriazole (Tinuvin 234, made by Ciba Geigy AG), and the like. The ultraviolet absorber of acrylate type includes for example, 2-ethylhexyl-2-cyano-3,3- diphenyl acrylate, ethyl-2-cyano-3,3-diphenyl acrylate, and the like. The ultraviolet absorber of salicylate type that may be used includes for example, phenyl salicylate, 4-t-butylphenyl salicylate, p-octylphenyl salicylate, and the like.
The thickness of the ultraviolet absorbing layer preferably is to be determined so as to make the reflectance of the ultraviolet absorbing layer with respect to ultraviolet light substantially zero. For example, in cases where the ultraviolet absorber used is Tinuvin emulsion and the ultraviolet wavelength of the light source is 254 nm, the thickness of the ultraviolet absorbing layer of no higher than 1 μm is sufficient enough and that of 0.1 to 1 μm range is suitable.
The ultraviolet absorbing layer may be formed on the fluorescent image-forming layer as an excitation-light shielding layer. In the area wherein the excitation-light shielding layer is formed, the irradiated ultraviolet light cannot reach the fluorescent image-forming layer, due to that they are absorbed by the excitation-light shielding layer, and hence light is not emitted therefrom. Consequently, by forming an area that forms the excitation-light shielding layer and another area that does not form the excitation-light shielding layer, an area that emits light and another area that does not emit light respectively can be formed, and thereby a fluorescent image can be formed. In this case, the fluorescent image may be formed by forming an excitation-light shielding layer along a pattern, on top of the fluorescent image forming-layer that has been so constructed as to uniformly emit light, or may be formed by forming the excitation-light shielding layer along a different pattern, on top of the fluorescent image-forming layer that has been formed along a certain pattern.
With respect to the protective layer, one having a high transparency to both visible light and ultraviolet light is preferred, and it can be formed by an over-laminating or over-coating method. The over laminate can be formed, by laminating a transparent film of, for example, polyethylene terephthalate, polyvinyl chloride), polyethylene, polypropylene, or the like using an ordinary method.
As for the over coat, the resins shown above as an example that constitutes the vehicle of the fluorescent luminous ink used in the fluorescent image-forming layer can be employed. In particular, a resin of photopolymerization-curable type or electron beam curable type wherein a solvent is not used is preferable, and for example, an acrylic resin may be used, which can be prepared by using the acrylic monomer or monomers. In addition, additives such as a polymerization initiator are contained therein as described above, and those additives having high transparency to visible light and ultraviolet light are to be suitably selected. As the upper most surface layer, an OP layer may be formed using an offset printing method such as a medium process.
As for the substrate, plastics such as polyvinyl chloride), nylon, cellulose diacetate, cellulose triacetate, polystyrene, polyethylene, polypropylene, polyester, polyimide, and polycarbonate, metals such as copper and aluminum, paper, impregnated paper, or the like, for example, can be used alone or in combination as a composite material. The substrate can be suitably selected from the materials in view of the physical properties required thereof, for example, physical strength, rigidity, hiding power, light non-transmitting property, and the like. The thickness of the substrate is normally from 0.005 to 5 mm.
In cases where a high-quality paper wherein a fluorescent whitening agent is normally added for the purpose of enhancing the whiteness thereof is used as the substrate according to the present invention, the fluorescent whitening agent glows in blue color upon irradiation of ultraviolet light using a black light. Consequently, upon irradiation of ultraviolet light for the purpose of identifying by sight the fluorescent image formed by the fluorescent substance contained in the fluorescent image-forming layer formed on the paper substrate, the fluorescent whitening agent contained in the paper substrate also emits light as well, which causes a problem that the detection of the image becomes difficult. Hence, it is preferable to choose a paper substrate that contains no, or least possible fluorescent whitening agent. It is effective to form an ultraviolet absorbing layer that contains for example, 10% of Tinuvin® (made by Ciba Specialty Chemicals Inc.) therein, printed on an under layer to suppress the influence of the fluorescent whitening agent, on the paper substrate. As for the means of irradiating an ultraviolet light that functions as the excitation light causing the fluorescent image to emerge, a variety of light sources emitting a specific wavelength of ultraviolet light can be chosen according to the species of the fluorescent substance described above. However, a small sized black light emitting the ultraviolet light of the wavelength of 365 nm is commercially available and can be used without difficulty. In addition, a germicidal lamp emitting the ultraviolet light of the wavelength of 254 nm may be used as well. Namely, it is preferable to choose fluorescent substances based on the above two wavelength ranges, due to that it makes the practice of the present invention easier.
Suitable fluorescent pigments can be broadly classified into two groups, namely one that emits light upon irradiation by ultraviolet light of 254 nm but does not emit light upon irradiation by ultraviolet light of 365 nm, and the other that emits light upon irradiation by ultraviolet light of each of 254 nm and 365 nm. The fluorescent image-forming layer according to the present invention comprises two species of fluorescent pigments, each emitting light of a mutually different wavelength range. By choosing two fluorescent substances each of which can be excited by a mutually different wavelength of ultraviolet light, a fluorescent image forming layer that develops a fluorescent image glowing in two different colors in response to the wavelength of ultraviolet light irradiated thereon, for example, a fluorescent image of one color upon irradiation of the ultraviolet light of 254 nm and that of another color upon irradiation of the ultraviolet light of 365 nm, can be formed.
Yet another aspect of the present invention relates to a method for counterfeit-proof marking of documents as originals in a variety of ways. For example, identification papers, passports, banknotes, cheques and share certificates can be marked as being originals. The method according to the invention can equally be used for creating counterfeit-proof product identification labels. The economic damage caused to the global economy by product piracy and counterfeit goods is immense. It is necessary particularly to prevent counterfeiting in the case of pharmaceutical products. The method according to the invention allows, for example, the counterfeit-proof marking of blister packs, so that it is possible to have a decisive effect in preventing inferior preparations being passed off as the original articles. There is extremely wide scope for use of the marking technology based on the method according to the invention. In addition to the labelling of branded products for mass consumption in order to ensure effective brand protection it is also possible for high-value goods that are at risk of counterfeiting, such as banknotes and chip cards, to be rendered counterfeit-proof in a simple and easily automated manner at relatively low cost. In the case of goods that are especially affected by product piracy, such as automotive spare parts, toys and CDs, it could be possible, in addition, to achieve copy protection that has been unachievable hitherto.
For example, an indicator strip comprising the inventive binary fluorescent pigment composition that is not visible under normal circumstances could be applied to a suitable substrate of a product or document to be protected against counterfeiting. Checking the authenticity of the article could then be effected very simply by irradiation (e.g. with a lamp that emits light of a suitable wavelength), so that the indicator strip would be visible to an observer or, in the event of a counterfeit, not visible to the observer. The authenticity of branded products could also be checked in this way. It might be possible for the reproduction of a mark on packaging to be so changed under the action of light of a certain intensity and/or a certain wavelength spectrum that a consumer would be in no doubt as to the origin of the goods. Limits will thus be set on brand and/or product piracy.
Examples
Fluorescent luminous inks 1-1 and I-2 were prepared, wherein in
(D Ll
Y(V1P)O4)Eu type fluorescent pigment that emits light of a red color and the BaMgAI10Oi7IEu, Mn type fluorescent pigment that emits light of a blue color, and in [N) L2
Y(V,P)O4:Eu type fluorescent pigment that emits light of a red color and the BaMg2AI16O27:Eu,Mn type fluorescent pigment that emits light of a green color, were incorporated. Both 1-1 and I-2 contain the two fluorescent pigments in a ratio of 50:50.
The final printing ink formulation comprises 4% 1-1 (or I-2) fluorescent pigment powder, and 96% Vinyl/ketone clear varnish.
The varnish formulation is a vinyl/ketone clear varnish of 14%Vinylite VYHH (vinyl coploymer resin), 10% Ethoxypropanol and 76% Methylethylketone.
Fluorescent pigment powders were first incorporated into the varnish by a pre-dispersing step in that a clear varnisch is prepared, then the fluorescent pigment powder is slowly added while stirring, followed by an additional stirring of 5 min at 15 m/s. The final dispersion was obtained in a Skandex apparatus using 2 mm glass beads for 30 min. The resulting ink was then printed with a conventional cylinder (0.35 g/m2 1-1 or I-2) on contrast paper to obtain a full shade rotogravure printing.
Fluorescence spectra of the light emissions from the fluorescent luminous ink 1-1 show that BaMgAI10Oi7:Eu,Mn type fluorescent pigment emits light of a blue color and the Y(V1P)O4)Eu type fluorescent pigment emits light of a red color.
Also, fluorescence spectra of the light emissions from the fluorescent luminous ink 1-2 show that BaMg2AI16C^Eu1Mn type fluorescent pigment emits light of a blue color and the Y(V,P)O4:Eu type fluorescent pigment emits light of a red color.
Since the fluorescent luminous ink and the respective fluorescent image comprise two species of fluorescent pigments, each of which emits light of a mutually different wavelength range, they are able to glow in a color not obtained before, and further can be caused to emit light of a different wavelength range, namely a different color upon changing the excitation wavelength, by choosing the species of fluorescent pigments excitable by a mutually different excitation wavelength. The security levels of printed matters requiring forgery prevention such as securities including a coupon and a prepaid card can be enhanced by judging the authenticity of the fluorescent luminous ink and the respective fluorescent image which have been so constituted as to emit light of different colors upon irradiating ultraviolet light of a mutually different wavelength, by irradiating thereon a plurality of ultraviolet light of a mutually different wavelength that can cause them to change the color of the emitting light.
A fluorescent luminous ink that emits light of a color not obtained before can be provided by incorporating therein two different fluorescent pigments each emitting light of a mutually different wavelength range. By choosing excitation wavelengths that can excite both of the two fluorescent pigments, the ink can be made to emit light of mutually different color, one upon irradiation by an ultraviolet light of the first wavelength, and the other upon irradiation by an ultraviolet light of the second wavelength.

Claims

Claims
1. A pigment composition comprising a first and a second inorganic fluorescent pigment that emit light upon irradiation by ultraviolet light, wherein the first fluorescent pigment emits light of a first wavelength in a visible light range upon irradiation by an ultraviolet light of a first wavelength and is substantially transparent to visible light, and the second fluorescent pigment that emits light of a second wavelength in a visible light range that is different from the first wavelength in a visible light range upon irradiation by an ultraviolet light of a second wavelength and is substantially transparent to visible light and wherein the first and the second inorganic fluorescent pigment have a particle size distribution of D90 < 5μm.
2. The pigment composition according to claim 1 , wherein the first and the second fluorescent pigment is selected from the group consisting of Ln2Os)Eu; Ln2VO4)Eu; Ln(V,P)O4:EU; Ln2(V,P,B)O4;Eu; Ln2VO4:Eu; Ln2(V,P)O4:Eu; Ln2(V,P,B)O4:Eu;
Y2O3:Eu; YV04:Eu; Y(V,P)O4:EU; Y(V,P,B)O4;Eu; YV04:Eu; Y(V,P)O4:Eu;
Y(V,P,B)O4;Eu; Mg4Ge05,5F:Mn; SrMg(SiO4)2:Eu,Mn; CaSnO4:Eu; Mg4(Ge,Sn)O5,5:Mn;
Y2O3 Eu; Ln2O3 Eu (Ln=Lanthanide), Gd(Zn, Mg)B5Oi0:Ce,Mn; (Y1Eu)W3Oi2;
ZnSiO4:Mn; (Ce1Tb)MgAI11Oi9; (Ce1Tb1Mn)MgAI11O19; LaPO4:Ce,Tb; Y2SiO5)Ce1Tb; MgGa2O4)Mn1 (Ba(Eu)(Mg(Mn)AI16O27; Zn2SiO4Tb; Y2O3; AI2O3Tb; Y3AI5O12Tb;
SrAI2O4:Eu; Y3AI5O12)Ce; Y3(AI1Ga)5O12)Ce; Sr3Ca2(PO4)3CI:Eu; (SrBaCa)5(PO4)3CI:Eu;
CaWO4; CaWO4)Pb; Ba1MgAI10O17)Eu1Mn, BaMg2AI16O27)Eu1Mn; Ba1MgAI10O17)Eu; and
BaMg2AI16O27)Eu.
3. The pigment composition according to claim 1 , wherein the first fluorescent pigment is Y(V1P)O4)Eu and the second fluorescent pigment is either BaMgAI10O17)Eu1Mn or BaMg2AI16O27)Eu1Mn.
4. The pigment composition according to any of claims 1 to 3, wherein the first and the second fluorescent pigment are present in equal amounts.
5. A product for forgery prevention comprising the pigment composition according to any of claims 1 to 4.
6. The product for forgery prevention according to claim 5 wherein said product is an ink further comprising an ink vehicle.
7. A fluorescent image formed by printing the product for forgery prevention according to claim 6 on a substrate comprising at least one fluorescent image-forming layer on said substrate, wherein the at least one fluorescent image-forming layer comprises a first fluorescent pigment that emits light of the first wavelength in a visible light range upon irradiation by the ultraviolet light of the first wavelength, and the second fluorescent pigment that emits light of the second wavelength in a visible light range being different from the above first wavelength in a visible light range upon irradiation by the ultraviolet light of the second wavelength and is substantially transparent to visible light.
8. A method for the counterfeit-proof labelling of products, which comprises the step of printing the product for forgery prevention according to claim 6 as product label onto a product or onto the packaging of a product.
PCT/EP2007/057305 2006-07-26 2007-07-16 Binary fluorescent pigment composition and its use for forgery and counterfeit prevention WO2008012225A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP06117887.7 2006-07-26
EP06117887 2006-07-26

Publications (1)

Publication Number Publication Date
WO2008012225A1 true WO2008012225A1 (en) 2008-01-31

Family

ID=37487414

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2007/057305 WO2008012225A1 (en) 2006-07-26 2007-07-16 Binary fluorescent pigment composition and its use for forgery and counterfeit prevention

Country Status (1)

Country Link
WO (1) WO2008012225A1 (en)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009008172B3 (en) * 2009-02-10 2010-07-01 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Material e.g. organic material, and semi-finished or end product e.g. package film, tamper-proof marking method, involves mixing fluorophore to material during synthesis or processing, and temporarily controlling fluorescence properties
DE102009024685A1 (en) 2009-06-12 2010-12-16 Gmbu E.V., Fachsektion Dresden Luminescent composite particle, useful e.g. as marking agent in polymeric films and articles for forgery-proof product identification, comprises organic optical brightener, which is homogeneously embedded in microspherical inorganic oxide
EP2295507A1 (en) * 2008-06-30 2011-03-16 Keio University Ink composition
FR2951110A1 (en) * 2009-10-14 2011-04-15 Herve Hollard DECORATION OR MARKING PROCESS ON PLASTIC AND METAL MATERIAL WITH SPECIAL EFFECT PIGMENTS
FR2953840A1 (en) * 2009-12-16 2011-06-17 Oberthur Technologies LANTHANIDE-BASED CODING PRODUCTS AND USES THEREOF
WO2011095948A1 (en) * 2010-02-08 2011-08-11 Koninklijke Philips Electronics N.V. Color adjusting arrangement
EP2684934A1 (en) 2012-07-09 2014-01-15 Commissariat A L'energie Atomique Et Aux Energies Alternatives Use of lanthanide complexes for the optical marking of products
EP2848661A1 (en) * 2013-09-17 2015-03-18 Sebastian G. Metzger Means and liquid mixture for visual marking objects and people and the production and use thereof
JP2016180807A (en) * 2015-03-23 2016-10-13 株式会社沖データ Image forming apparatus
US9710834B2 (en) 2010-06-02 2017-07-18 International Business Machines Corporation Pre and post purchase identification of counterfeit products
US9727902B2 (en) 2010-06-02 2017-08-08 International Business Machines Corporation Mitigating distribution and consumption of counterfeit products
US9727899B2 (en) 2010-06-02 2017-08-08 International Business Machines Corporation Manufacturing and distribution to avoid counterfeit products
CN113388398A (en) * 2021-06-11 2021-09-14 厦门理工学院 Eu (Eu)3+Rare earth yttrium-based tungstate doped fluorescent powder and preparation method thereof
EP3974483A1 (en) * 2020-09-29 2022-03-30 Gleitsmann Security Inks GmbH Security ink and security article, such as a banknote, with a tri-luminescent effect

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5005873A (en) * 1986-04-07 1991-04-09 West Michael A Marking of articles
US20020063301A1 (en) * 2000-09-21 2002-05-30 Tetsuya Hanamoto Semiconductor light-emitting device and light-emitting display device therewith
US20040251833A1 (en) * 2003-06-12 2004-12-16 Nec Plasma Display Corporation Plasma display apparatus and fluorescent material for plasma display panel
WO2006072919A2 (en) * 2005-01-10 2006-07-13 Philips Intellectual Property & Standards Gmbh Illumination system comprising barium magnesium aluminate phosphor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5005873A (en) * 1986-04-07 1991-04-09 West Michael A Marking of articles
US20020063301A1 (en) * 2000-09-21 2002-05-30 Tetsuya Hanamoto Semiconductor light-emitting device and light-emitting display device therewith
US20040251833A1 (en) * 2003-06-12 2004-12-16 Nec Plasma Display Corporation Plasma display apparatus and fluorescent material for plasma display panel
WO2006072919A2 (en) * 2005-01-10 2006-07-13 Philips Intellectual Property & Standards Gmbh Illumination system comprising barium magnesium aluminate phosphor

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2295507A1 (en) * 2008-06-30 2011-03-16 Keio University Ink composition
CN102105543A (en) * 2008-06-30 2011-06-22 学校法人庆应义塾 Ink composition
EP2295507A4 (en) * 2008-06-30 2012-10-31 Univ Keio Ink composition
DE102009008172B3 (en) * 2009-02-10 2010-07-01 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Material e.g. organic material, and semi-finished or end product e.g. package film, tamper-proof marking method, involves mixing fluorophore to material during synthesis or processing, and temporarily controlling fluorescence properties
DE102009024685A1 (en) 2009-06-12 2010-12-16 Gmbu E.V., Fachsektion Dresden Luminescent composite particle, useful e.g. as marking agent in polymeric films and articles for forgery-proof product identification, comprises organic optical brightener, which is homogeneously embedded in microspherical inorganic oxide
FR2951110A1 (en) * 2009-10-14 2011-04-15 Herve Hollard DECORATION OR MARKING PROCESS ON PLASTIC AND METAL MATERIAL WITH SPECIAL EFFECT PIGMENTS
WO2011045541A1 (en) * 2009-10-14 2011-04-21 Hollard Herve Decorating or marking method
FR2953840A1 (en) * 2009-12-16 2011-06-17 Oberthur Technologies LANTHANIDE-BASED CODING PRODUCTS AND USES THEREOF
WO2011080461A1 (en) * 2009-12-16 2011-07-07 Oberthur Technologies Lanthanide-based coding products and use thereof
WO2011095948A1 (en) * 2010-02-08 2011-08-11 Koninklijke Philips Electronics N.V. Color adjusting arrangement
US9727902B2 (en) 2010-06-02 2017-08-08 International Business Machines Corporation Mitigating distribution and consumption of counterfeit products
US9710834B2 (en) 2010-06-02 2017-07-18 International Business Machines Corporation Pre and post purchase identification of counterfeit products
US9727899B2 (en) 2010-06-02 2017-08-08 International Business Machines Corporation Manufacturing and distribution to avoid counterfeit products
US9234131B2 (en) 2012-07-09 2016-01-12 Commissariat A L'energie Atomique Et Aux Energies Alternatives Use of lanthanide complexes for optical marking of products
EP2684934A1 (en) 2012-07-09 2014-01-15 Commissariat A L'energie Atomique Et Aux Energies Alternatives Use of lanthanide complexes for the optical marking of products
EP2848661A1 (en) * 2013-09-17 2015-03-18 Sebastian G. Metzger Means and liquid mixture for visual marking objects and people and the production and use thereof
JP2016180807A (en) * 2015-03-23 2016-10-13 株式会社沖データ Image forming apparatus
EP3974483A1 (en) * 2020-09-29 2022-03-30 Gleitsmann Security Inks GmbH Security ink and security article, such as a banknote, with a tri-luminescent effect
WO2022069127A1 (en) * 2020-09-29 2022-04-07 Gleitsmann Security Inks Gmbh Security ink and security article, such as a banknote, with a tri-luminescent effect
CN113388398A (en) * 2021-06-11 2021-09-14 厦门理工学院 Eu (Eu)3+Rare earth yttrium-based tungstate doped fluorescent powder and preparation method thereof

Similar Documents

Publication Publication Date Title
WO2008012225A1 (en) Binary fluorescent pigment composition and its use for forgery and counterfeit prevention
EP2207854B1 (en) Security element
JPH10251570A (en) Fluorescent luminous ink and fluorescent image formed product
JP3828632B2 (en) Fluorescent image formation
RU2371322C2 (en) Machine-readable protective element for protected products
US20080290649A1 (en) Laser Transfer of Security Features
US20050031838A1 (en) Taggant security system for paper products as a deterrent to counterfeiting
JP7066939B2 (en) Low energy curable offset and letterpress printing inks and printing processes
KR102434303B1 (en) Low energy curable offset and letterpress printing inks and printing methods
JPH10315605A (en) Fluorescent image forming material and fluorescent image reader
JPH10320499A (en) Device for reading fluorescent picture
AU2008213463A1 (en) Safety and/or valuable document having a photonic crystal
CN114829511B (en) UV-LED radiation-curable offset printing ink and printing method
JP4138082B2 (en) Intermediate transfer recording medium and printed matter
JPH0952479A (en) Information carrying sheet, ink to be used therefor, and transfer sheet
JP5464540B2 (en) Printed matter with mixed color fluorescence
JPH10250211A (en) Fluorescent image formed material
US11926747B2 (en) UV curable and heat sealable ink
JP4240963B2 (en) Hologram transfer sheet and hologram transfer medium
JPH10250212A (en) Image printed matter and fluorescent image forming device
EP3317862B1 (en) Postage stamps
US20230331021A1 (en) Multilayer body and method for producing a multilayer body
JP7323165B2 (en) Lid material for PTP package
JP2004098561A (en) Forgery-proof card

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 07787573

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

NENP Non-entry into the national phase

Ref country code: RU

122 Ep: pct application non-entry in european phase

Ref document number: 07787573

Country of ref document: EP

Kind code of ref document: A1